Phosphor Wheel Back-Surface Diffusion for Projection Color Purity

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Solution Overview

Problem

The conventional light source devices for projection-type video display devices suffer from color mixing issues due to backward traveling blue light reflecting off the phosphor wheel's back surface, causing interference with fluorescent light.

Innovation Solution

Incorporating a light processing region with a diffusion layer on the back surface of the phosphor wheel to diffuse and suppress backward traveling blue light, preventing its reflection and subsequent color mixing with fluorescent light.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a phosphor wheel with opening is used to generate fluorescent light, then color generation capability is improved, but backward traveling blue light reflects off the back surface causing color mixing

Engineering Contradiction:

Improvefluorescent light outputVSAvoidcolor mixing from return light

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

A light processing region is introduced as an intermediary element between the phosphor layer and the back surface of the substrate. This light processing region absorbs or scatters the backward traveling blue light before it can reflect off the back surface and cause color mixing with the fluorescent light output.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention converts the harmful backward traveling blue light into a beneficial effect by using the light processing region to absorb or scatter it. The previously harmful reflection is transformed into controlled light management, preventing color mixing while maintaining fluorescent light generation efficiency.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Productivity

If the phosphor wheel back surface is made reflective, then light extraction efficiency is improved, but return light mixes with fluorescent light reducing color purity

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoidcolor purity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The invention applies different optical properties to different regions of the phosphor wheel structure. The phosphor layer maintains its fluorescent conversion properties while the light processing region on the back surface is specifically designed to absorb or scatter blue light. This local differentiation allows simultaneous optimization of light extraction and color purity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The phosphor wheel is segmented into functionally distinct regions: the phosphor layer for fluorescent light generation and the light processing region for managing backward traveling blue light. This segmentation allows each region to be optimized for its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

3Illumination intensity

If a relay optical system is used to combine blue light and fluorescent light, then combined light output is improved, but backward traveling light causes color mixing

Engineering Contradiction:

Improvecombined light outputVSAvoidcolor mixing in combined light

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The light processing region performs preliminary action by absorbing or scattering the backward traveling blue light before it can complete the optical path and mix with the fluorescent light in the combined light output. This preventive measure is implemented upstream in the optical path to eliminate the color mixing problem at its source.

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration enhances color purity by reducing the residual ratio of return light in fluorescent light, allowing for high-quality color output.

Implementation Method 1

a phosphor region provided on a first surface of the substrate, the phosphor region having phosphor that converts light from the excitation light source into fluorescent light

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Implementation Method 2

a light processing region provided on a second surface of the substrate at a position corresponding, in a front-back direction, to the phosphor region

Methodology Applied

Scientific EffectLight diffusion: Scattering

Data Source

PatentUS20260029701A1Light source device and projection-type video display device

Publication Date: 2026.01.29 PANASONIC PROJECTOR & DISPLAY CORPORATION

AI summary

A light source device includes: an excitation light source; a phosphor wheel; a light guide optical system; and a color wheel, wherein the phosphor wheel includes: a substrate; a phosphor region provided on a first surface of the substrate, the phosphor region having phosphor that converts light from the excitation light source into fluorescent light; and a light processing region provided on a second surface of the substrate at a position corresponding, in a front-back direction, to the phosphor region; an opening provided from the first surface to the second surface of the substrate; and a drive device that rotates the substrate.